An estimated 41,000 people in the United States live with an upper limb loss at or above the wrist. The loss of a limb by an individual can profoundly limit everyday activities such as dressing, eating, and performing personal hygiene tasks. The loss of a limb may also affect social interactions and personal relationships and in some cases can threaten the basic independence of the individual. Further, the individual can experience difficulty in grasping and holding objects which may impede leisure activities, such as reading or playing sports. The inability to properly operate a prosthetic by the individual may also prevent performance of certain employment tasks or severely limit future job prospects, thereby impacting a person's financial security, sense of identity and purpose, and overall quality of life.
Conventional passive prosthetic devices may be very lightweight and relatively inexpensive to manufacture; however, such prosthetic devices provide very limited function. Body-powered devices are generally light, robust, functional, and inexpensive. The majority of these devices have a voluntary-open (VO) mode of operation, while several others have a voluntary-closing (VC) mode of operation. A few devices have both a VO and a VC mode of operation. However, these devices are complex and require altering the initial positions of the jaws and the direction of movement, without altering the direction of movement and starting position of a Bowden cable attachment. As such, there remains a need for a gripping device or similar prosthetic device that can quickly and easily switch between voluntary-open and voluntary modes of operation without extensive adjustments.